/Engine/Source/Runtime/Engine/Public/RawIndexBuffer.h
Forces (or not) usage of 32 bits indices. No validation is made as to whether Indices can all be stored in 16 bits indices (if bIn32Bit == false) or not : use only if you know the max value in Indices, otherwise, use ComputeIndexWidth
void ForceUse32Bit ( bool bIn32Bit )